1. Field of the Invention
The present invention relates to a solid-state imager, a method of manufacturing the same, and a camera. More specifically, the present invention relates to a solid-state imager including a photoelectric conversion region for photoelectrically converting a light beam received on a light receiving surface thereof into a signal charge, and a waveguide path for guiding the light beam to the light receiving surface. The present invention also relates to a method for manufacturing the solid-state imager and a camera including the solid-state imager.
2. Description of the Related Art
Cameras, such as a digital video camera and a digital still camera, include a solid-state imager. The solid-state imagers includes a complementary metal oxide semiconductor (CMOS) image sensor, and a charge-coupled device (CCD), for example.
In the solid-state imager, an imaging region composed of a plurality of pixels is arranged on the surface of a semiconductor substrate. A plurality of photoelectric conversion regions arranged respectively for a plurality of pixels in the imaging region receive a light beam of a subject image and generates a signal charge by photoelectrically converting the received light beam. For example, a photodiode serves as the photoelectric conversion region.
In the solid-state imager, the photoelectric conversion region such as a photodiode receives on a light receiving surface thereof a light beam collected by a micro lens as disclosed in Japanese Patent No. 2600250 and Japanese Unexamined Patent Application Publication No. 2003-273342.
The use of a “pupil correction” technique adjusts the positional relationship between the micro lens and the light receiving surface of the photoelectric conversion region.
The solid-state imager includes a waveguide path for each pixel in order to increase the collection efficiency of light, and thus gain of the imager.
The waveguide path guides light collected by the micro lens to the light receiving surface of the photoelectric conversion region.
More specifically, the waveguide path has a core section constructed of an optical material having a high refraction index and guiding the light. The waveguide path also includes a clad section having a refraction index lower than that of the core section and surrounds the core section. The waveguide path thus totally reflects light on the border between the core section and the clad section. The waveguide path increases the collection efficiency of light, leading to high gain. Reference is made to Japanese Unexamined Patent Application Publication Nos. 2004-221532, and 2006-261247, and “CMOS Imager with Copper Wiring and Lightpipe,” 2006 IEDM Technical Digest Session 5.5, J. Gambino et. al.
For example, the waveguide path is produced by laminating a member functioning as a clad on a substrate bearing a photoelectric conversion region, arranging an aperture in the laminate body so that a light receiving surface of the photoelectric conversion region is exposed and filling the aperture with an optical material having a high refraction index.